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Is there any way of cyclic rotation of 2-D lines in opengl

I want to make cyclic rotation of these 2-D lines such that when mouse is scrolled the lines move in upward or downward direction. For ex:- if mouse wheel is scrolled upward line at the top moves to the bottom and all lines move upward.
I am able to do this by changing data but it is a slow process.
Is there any way to do this using shader in OpenGl.
code:-
import OpenGL.GL as gl
import OpenGL.arrays.vbo as glvbo
from PyQt5.Qt import *
import numpy as np
import sys
import copy
VS1 = '''
#version 450
layout(location = 0) in vec2 position;
uniform float right;
uniform float bottom;
uniform float left;
uniform float top;
void main() {
const float far = 1.0;
const float near = -1.0;
mat4 testmat = mat4(
vec4(2.0 / (right - left), 0, 0, 0),
vec4(0, 2.0 / (top - bottom), 0, 0),
vec4(0, 0, -2.0 / (far - near), 0),
vec4(-(right + left) / (right - left), -(top + bottom) / (top - bottom), -(far + near) / (far - near), 1)
);
gl_Position = testmat * vec4(position.x, position.y, 0., 1.);
}
'''
FS1 = '''
#version 450
// Output variable of the fragment shader, which is a 4D vector containing the
// RGBA components of the pixel color.
uniform vec3 triangleColor;
out vec4 outColor;
void main()
{
outColor = vec4(triangleColor, 1.0);
}
'''
def compile_vertex_shader(source):
"""Compile a vertex shader from source."""
vertex_shader = gl.glCreateShader(gl.GL_VERTEX_SHADER)
gl.glShaderSource(vertex_shader, source)
gl.glCompileShader(vertex_shader)
# check compilation error
result = gl.glGetShaderiv(vertex_shader, gl.GL_COMPILE_STATUS)
if not (result):
raise RuntimeError(gl.glGetShaderInfoLog(vertex_shader))
return vertex_shader
def compile_fragment_shader(source):
"""Compile a fragment shader from source."""
fragment_shader = gl.glCreateShader(gl.GL_FRAGMENT_SHADER)
gl.glShaderSource(fragment_shader, source)
gl.glCompileShader(fragment_shader)
result = gl.glGetShaderiv(fragment_shader, gl.GL_COMPILE_STATUS)
if not (result):
raise RuntimeError(gl.glGetShaderInfoLog(fragment_shader))
return fragment_shader
def link_shader_program(vertex_shader, fragment_shader):
"""Create a shader program with from compiled shaders."""
program = gl.glCreateProgram()
gl.glAttachShader(program, vertex_shader)
gl.glAttachShader(program, fragment_shader)
gl.glLinkProgram(program)
result = gl.glGetProgramiv(program, gl.GL_LINK_STATUS)
if not (result):
raise RuntimeError(gl.glGetProgramInfoLog(program))
return program
class GLPlotWidget(QGLWidget):
def __init__(self, *args):
super(GLPlotWidget, self).__init__()
self.width, self.height = 100, 100
self.we = np.load('two.npy', mmap_mode='r')
self.e = copy.deepcopy(self.we[:, :, :])
self.w = copy.deepcopy(self.we[:, :, :])
for i in range(0, 24):
self.w[i, :, 1] = self.e[i, :, 1] - np.array(9999 * i)
# self.e[:, :, 1] = np.interp(self.e[:, :, 1], (self.e[:, :, 1].min(), self.e[:, :, 1].max()),
# (-1, 1))
#
# self.e[:, :, 0] = np.interp(self.e[:, :, 0], (self.e[:, :, 0].min(), self.e[:, :, 0].max()),
# (-1, +1))
self.right, self.left, self.top, self.bottom = self.e[0, -1, 0], self.e[
0, 0, 0], self.e[0, :, 1].max(), self.e[-1, :, 1].min()
self.vbo = glvbo.VBO(self.e)
self.count = self.vbo.shape[1]
self.scroll = 0
self.number_of_arm = 24
self.sensor_list_const = np.array(range(0, self.number_of_arm))
self.sensor_list_roll = copy.deepcopy(self.sensor_list_const)
self.showMaximized()
def initializeGL(self):
vs = compile_vertex_shader(VS1)
fs = compile_fragment_shader(FS1)
self.shaders_program_plot = link_shader_program(vs, fs)
def ortho_view(self, i):
right = gl.glGetUniformLocation(i, "right")
gl.glUniform1f(right, self.right)
left = gl.glGetUniformLocation(i, "left")
gl.glUniform1f(left, self.left)
top = gl.glGetUniformLocation(i, "top")
gl.glUniform1f(top, self.top)
bottom = gl.glGetUniformLocation(i, "bottom")
gl.glUniform1f(bottom, self.bottom)
def paintGL(self):
self.resizeGL(self.width, self.height)
gl.glClearColor(0.75, 0.75, 0.75, 0)
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)
gl.glEnable(gl.GL_DEPTH_TEST)
self.vbo.bind()
gl.glEnableVertexAttribArray(0)
gl.glVertexAttribPointer(0, 2, gl.GL_FLOAT, gl.GL_FALSE, 0, None)
gl.glUseProgram(self.shaders_program_plot)
self.ortho_view(self.shaders_program_plot)
uni_color = gl.glGetUniformLocation(self.shaders_program_plot, "triangleColor")
for i in range(0, self.vbo.data.shape[0]):
gl.glUniform3f(uni_color, 0, 0, 0)
gl.glLineWidth(1)
gl.glDrawArrays(gl.GL_LINE_STRIP, i * self.count, self.count)
self.vbo.unbind()
# self.greyscale()
# gl.glUseProgram(0)
def reset_vbo(self):
self.wex = copy.deepcopy(self.w)
for i, j in zip(self.sensor_list_roll, self.sensor_list_const):
self.wex[j, :, 1] = self.w[j, :, 1] + np.array(9999 * (self.number_of_arm - i))
self.vbo.set_array(self.wex)
self.right, self.left, self.top, self.bottom = self.wex[0, -1, 0], self.wex[
0, 0, 0], self.wex[:, :, 1].max(), self.wex[:, :, 1].min()
self.update()
def resizeGL(self, width, height):
self.width, self.height = width, height
gl.glViewport(0, 0, width, height)
def wheelEvent(self, *args, **kwargs):
event = args[0]
# print(event.angleDelta().y())
if event.angleDelta().y() > 0:
self.scroll = self.scroll - 1
else:
self.scroll = self.scroll + 1
if self.scroll > self.number_of_arm - 1 or self.scroll < -(self.number_of_arm - 1):
self.scroll = 0
self.sensor_list_roll = np.roll(self.sensor_list_const, self.scroll)
# self.patch_move(event)
self.reset_vbo()
def main():
app = QApplication(sys.argv)
editor = GLPlotWidget()
editor.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
data file :- https://drive.google.com/file/d/1y6w35kuMguR1YczK7yMJpXU86T6qtGSv/view?usp=sharing

You can use the uniforms top and bottom to scroll the view. You have to set the individually for each line.
Compute the scroll factor self.scroll dependent on the y scale of the projection:
class GLPlotWidget(QGLWidget):
# [...]
def wheelEvent(self, *args, **kwargs):
event = args[0]
scroll_scale = 0.01
size = self.top - self.bottom
if event.angleDelta().y() > 0:
self.scroll = self.scroll - size * scroll_scale
if self.scroll < 0:
self.scroll += size
else:
self.scroll = self.scroll + size * scroll_scale
if self.scroll > size:
self.scroll -= size
Further more you have to now the y range of each line. Compute the minimum and maximum for each line and store it to a list (self.linerange):
class GLPlotWidget(QGLWidget):
def __init__(self, *args):
# [...]
self.linerange = [(self.e[li, :, 1].max(), self.e[-li, :, 1].min()) for li in range(self.vbo.shape[0])]
Shift self.top and self.bottom by self.scroll for each line:
top, bottom = self.top+self.scroll, self.bottom+self.scroll
If the line would "fall out" of the window at the bottom, then lift it to the top of the view:
if self.linerange[i][0]-self.scroll < self.bottom:
top, bottom = top-size, bottom-size
Complete paintGL method:
class GLPlotWidget(QGLWidget):
# [...]
def paintGL(self):
self.resizeGL(self.width, self.height)
gl.glClearColor(0.75, 0.75, 0.75, 0)
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)
gl.glEnable(gl.GL_DEPTH_TEST)
self.vbo.bind()
gl.glEnableVertexAttribArray(0)
gl.glVertexAttribPointer(0, 2, gl.GL_FLOAT, gl.GL_FALSE, 0, None)
gl.glUseProgram(self.shaders_program_plot)
self.ortho_view(self.shaders_program_plot)
uni_color = gl.glGetUniformLocation(self.shaders_program_plot, "triangleColor")
loc_top = gl.glGetUniformLocation(self.shaders_program_plot, "top")
loc_bottom = gl.glGetUniformLocation(self.shaders_program_plot, "bottom")
for i in range(0, self.vbo.data.shape[0]):
size = self.top - self.bottom
top, bottom = self.top+self.scroll, self.bottom+self.scroll
if self.linerange[i][0]-self.scroll < self.bottom:
top, bottom = top-size, bottom-size
gl.glUniform1f(loc_top, top)
gl.glUniform1f(loc_bottom, bottom)
gl.glUniform3f(uni_color, 0, 0, 0)
gl.glLineWidth(1)
gl.glDrawArrays(gl.GL_LINE_STRIP, i * self.count, self.count)
self.vbo.unbind()

Best method to rotate triangles such that there is no gap between top and bottom line triangles after a full rotation?

I have created these triangles to form the greyscale surface of 2-D line plot. Now when I am rotating it using mouse wheel event, there is a gap between the top and bottom line and I want to remove it. Also the program run very slow after using this for loop in greyscale function. Can anyone suggest me any method or way to optimize this and make it work correctly?
code:-
import OpenGL.GL as gl
import OpenGL.arrays.vbo as glvbo
from PyQt5.Qt import *
import numpy as np
import sys
import copy
VS1 = '''
#version 450
layout(location = 0) in vec2 position;
uniform float right;
uniform float bottom;
uniform float left;
uniform float top;
void main() {
const float far = 1.0;
const float near = -1.0;
mat4 testmat = mat4(
vec4(2.0 / (right - left), 0, 0, 0),
vec4(0, 2.0 / (top - bottom), 0, 0),
vec4(0, 0, -2.0 / (far - near), 0),
vec4(-(right + left) / (right - left), -(top + bottom) / (top - bottom), -(far + near) / (far - near), 1)
);
gl_Position = testmat * vec4(position.x, position.y, 0., 1.);
}
'''
FS1 = '''
#version 450
// Output variable of the fragment shader, which is a 4D vector containing the
// RGBA components of the pixel color.
uniform vec3 triangleColor;
out vec4 outColor;
void main()
{
outColor = vec4(triangleColor, 1.0);
}
'''
VS = '''
#version 450
attribute vec2 position;
attribute vec3 a_Color;
uniform float right;
uniform float bottom;
uniform float left;
uniform float top;
out vec3 g_color;
void main() {
const float far = 1.0;
const float near = -1.0;
mat4 testmat = mat4(
vec4(2.0 / (right - left), 0, 0, 0),
vec4(0, 2.0 / (top - bottom), 0, 0),
vec4(0, 0, -2.0 / (far - near), 0),
vec4(-(right + left) / (right - left), -(top + bottom) / (top - bottom), -(far + near) / (far - near), 1)
);
gl_Position = testmat * vec4(position.x, position.y, 0., 1.);
g_color = a_Color;
}
'''
FS = '''
#version 450
// Output variable of the fragment shader, which is a 4D vector containing the
// RGBA components of the pixel color.
in vec3 g_color;
out vec4 outColor;
void main()
{
outColor = vec4(g_color, 1.0);
}
'''
def compile_vertex_shader(source):
"""Compile a vertex shader from source."""
vertex_shader = gl.glCreateShader(gl.GL_VERTEX_SHADER)
gl.glShaderSource(vertex_shader, source)
gl.glCompileShader(vertex_shader)
# check compilation error
result = gl.glGetShaderiv(vertex_shader, gl.GL_COMPILE_STATUS)
if not (result):
raise RuntimeError(gl.glGetShaderInfoLog(vertex_shader))
return vertex_shader
def compile_fragment_shader(source):
"""Compile a fragment shader from source."""
fragment_shader = gl.glCreateShader(gl.GL_FRAGMENT_SHADER)
gl.glShaderSource(fragment_shader, source)
gl.glCompileShader(fragment_shader)
result = gl.glGetShaderiv(fragment_shader, gl.GL_COMPILE_STATUS)
if not (result):
raise RuntimeError(gl.glGetShaderInfoLog(fragment_shader))
return fragment_shader
def link_shader_program(vertex_shader, fragment_shader):
"""Create a shader program with from compiled shaders."""
program = gl.glCreateProgram()
gl.glAttachShader(program, vertex_shader)
gl.glAttachShader(program, fragment_shader)
gl.glLinkProgram(program)
result = gl.glGetProgramiv(program, gl.GL_LINK_STATUS)
if not (result):
raise RuntimeError(gl.glGetProgramInfoLog(program))
return program
class GLPlotWidget(QGLWidget):
def __init__(self, *args):
super(GLPlotWidget, self).__init__()
self.width, self.height = 100, 100
self.we = np.load('two.npy', mmap_mode='r')
self.e = copy.deepcopy(self.we[:, :, :])
self.right, self.left, self.top, self.bottom = self.e[0, -1, 0], self.e[
0, 0, 0], self.e[0, :, 1].max(), self.e[-1, :, 1].min()
self.vbo = glvbo.VBO(self.e)
self.count = self.vbo.shape[1]
self.scroll = 0
self.number_of_arm = 24
self.linerange = [(self.e[li, :, 1].max(), self.e[-li, :, 1].min()) for li in range(self.vbo.shape[0])]
self.showMaximized()
def initializeGL(self):
vs = compile_vertex_shader(VS1)
fs = compile_fragment_shader(FS1)
self.shaders_program_plot = link_shader_program(vs, fs)
self.greyscale_data()
def greyscale_data(self):
self.color = np.zeros((self.e.shape[1] * (self.e.shape[0]), 3), dtype=np.float32)
for i in range(0, 24):
a = self.e[i, :, 1].min()
b = self.e[i, :, 1].max()
c = np.interp(self.e[i, :, 1], (a, b), (0.15, 0.85))
self.color[self.e.shape[1] * i:self.e.shape[1] * (i + 1), 0] = c
self.color[self.e.shape[1] * i:self.e.shape[1] * (i + 1), 1] = c
self.color[self.e.shape[1] * i:self.e.shape[1] * (i + 1), 2] = c
self.elems = []
b = self.e.shape[1] # number of points per line
a = self.e.shape[0] # total number of arms
for i in range(0, a):
if i < a-1:
for j in range(0, b - 1):
self.elems += [j + b * i, j + b * i + 1, j + b * (i + 1)]
self.elems += [j + b * (i + 1), j + b * (i + 1) + 1, j + b * i + 1]
else:
for j in range(0, b - 1):
self.elems += [j + b * i, j + b * i + 1, j]
self.elems += [j, j + 1, j + b * i + 1]
self.elems = np.array(self.elems, dtype=np.int32)
# print(self.elems[0:100])
vs = compile_vertex_shader(VS)
fs = compile_fragment_shader(FS)
self.shaders_program = link_shader_program(vs, fs)
self.vertexbuffer = gl.glGenBuffers(1)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self.vertexbuffer)
gl.glBufferData(gl.GL_ARRAY_BUFFER, self.e, gl.GL_DYNAMIC_DRAW)
self.elementbuffer = gl.glGenBuffers(1)
gl.glBindBuffer(gl.GL_ELEMENT_ARRAY_BUFFER, self.elementbuffer)
gl.glBufferData(gl.GL_ELEMENT_ARRAY_BUFFER, self.elems, gl.GL_DYNAMIC_DRAW)
self.colorbuffer = gl.glGenBuffers(1)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self.colorbuffer)
gl.glBufferData(gl.GL_ARRAY_BUFFER, self.color, gl.GL_DYNAMIC_DRAW)
def ortho_view(self, i):
right = gl.glGetUniformLocation(i, "right")
gl.glUniform1f(right, self.right)
left = gl.glGetUniformLocation(i, "left")
gl.glUniform1f(left, self.left)
top = gl.glGetUniformLocation(i, "top")
gl.glUniform1f(top, self.top)
bottom = gl.glGetUniformLocation(i, "bottom")
gl.glUniform1f(bottom, self.bottom)
def greyscale(self):
gl.glUseProgram(self.shaders_program)
self.ortho_view(self.shaders_program)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self.vertexbuffer)
stride = 0 # 3*self.e.itemsize
offset = None # ctypes.c_void_p(0)
loc = gl.glGetAttribLocation(self.shaders_program, 'position')
gl.glEnableVertexAttribArray(loc)
gl.glVertexAttribPointer(loc, 2, gl.GL_FLOAT, False, stride, offset)
gl.glBindBuffer(gl.GL_ELEMENT_ARRAY_BUFFER, self.elementbuffer)
loc = gl.glGetAttribLocation(self.shaders_program, 'a_Color')
gl.glEnableVertexAttribArray(loc)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self.colorbuffer)
gl.glVertexAttribPointer(loc, 3, gl.GL_FLOAT, False, stride, offset)
loc_top1 = gl.glGetUniformLocation(self.shaders_program, "top")
loc_bottom1 = gl.glGetUniformLocation(self.shaders_program, "bottom")
for i in range(0, 24):
size = self.top - self.bottom
top, bottom = self.top + self.scroll, self.bottom + self.scroll
if self.linerange[i][0] - self.scroll < self.bottom:
top, bottom = top - size, bottom - size
gl.glUniform1f(loc_top1, top)
gl.glUniform1f(loc_bottom1, bottom)
a = int(i * self.elems.size)
b = int((i+1) * self.elems.size)
c = int(self.elems.size/24)
# gl.glDrawElements(gl.GL_TRIANGLE_STRIP, self.elems.size, gl.GL_UNSIGNED_INT, None)
gl.glDrawRangeElements(gl.GL_TRIANGLE_STRIP, a, b, self.elems.size, gl.GL_UNSIGNED_INT, None)
def paintGL(self):
self.resizeGL(self.width, self.height)
gl.glClearColor(1, 1, 1, 0)
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)
gl.glEnable(gl.GL_DEPTH_TEST)
self.vbo.bind()
gl.glEnableVertexAttribArray(0)
gl.glVertexAttribPointer(0, 2, gl.GL_FLOAT, gl.GL_FALSE, 0, None)
gl.glUseProgram(self.shaders_program_plot)
self.ortho_view(self.shaders_program_plot)
uni_color = gl.glGetUniformLocation(self.shaders_program_plot, "triangleColor")
loc_top = gl.glGetUniformLocation(self.shaders_program_plot, "top")
loc_bottom = gl.glGetUniformLocation(self.shaders_program_plot, "bottom")
for i in range(0, self.vbo.data.shape[0]):
size = self.top - self.bottom
top, bottom = self.top + self.scroll, self.bottom + self.scroll
if self.linerange[i][0] - self.scroll < self.bottom:
top, bottom = top - size, bottom - size
gl.glUniform1f(loc_top, top)
gl.glUniform1f(loc_bottom, bottom)
gl.glUniform3f(uni_color, 0, 0, 0)
gl.glLineWidth(1)
gl.glDrawArrays(gl.GL_LINE_STRIP, i * self.count, self.count)
self.vbo.unbind()
self.greyscale()
# gl.glUseProgram(0)
def resizeGL(self, width, height):
self.width, self.height = width, height
gl.glViewport(0, 0, width, height)
def wheelEvent(self, *args, **kwargs):
event = args[0]
scroll_scale = 0.01
size = self.top - self.bottom
if event.angleDelta().y() > 0:
self.scroll = self.scroll - size * scroll_scale
if self.scroll < 0:
self.scroll += size
else:
self.scroll = self.scroll + size * scroll_scale
if self.scroll > size:
self.scroll -= size
self.update()
def main():
app = QApplication(sys.argv)
editor = GLPlotWidget()
editor.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
data file:- https://drive.google.com/file/d/1y6w35kuMguR1YczK7yMJpXU86T6qtGSv/view?usp=sharing

Add a straight line at the at the bin and the end of the data.
Compute the minimum and the maximum of the original data, the y scale of the data and the average offset from one line to another:
origshape = self.e.shape[:]
origmin, origmax = self.e[0, :, 1].max(), self.e[-1, :, 1].min()
origsize = origmax - origmin
origoffset = origsize / origshape[0]
Compute a new minimum and maximum with an certain offset (origoffset/2) and add a straight line at the begin and the end. Copy the first and last line and change the y component of the new lines by newmax respectively newmin
newmin, newmax = origmin - origoffset/2, origmax + origoffset/2
self.first = self.e[0,:,:].copy().reshape((1, *origshape[1:]))
self.last = self.e[-1,:,:].copy().reshape((1, *origshape[1:]))
self.first[:,:,1] = newmax
self.last[:,:,1] = newmin
self.e = np.concatenate((self.first, self.e, self.last))
New constructor of GLPlotWidget:
class GLPlotWidget(QGLWidget):
def __init__(self, *args):
super(GLPlotWidget, self).__init__()
self.width, self.height = 100, 100
self.we = np.load('two.npy', mmap_mode='r')
self.e = copy.deepcopy(self.we[:, :, :])
origshape = self.e.shape[:]
origmin, origmax = self.e[-1, :, 1].min(), self.e[1, :, 1].max()
origsize = origmax - origmin
origoffset = origsize / origshape[0]
newmin, newmax = origmin - origoffset/2, origmax + origoffset/2
self.first = self.e[0,:,:].copy().reshape((1, *origshape[1:]))
self.last = self.e[-1,:,:].copy().reshape((1, *origshape[1:]))
self.first[:,:,1] = newmax
self.last[:,:,1] = newmin
self.e = np.concatenate((self.first, self.e, self.last))
self.right, self.left, self.top, self.bottom = self.e[0, -1, 0], self.e[
0, 0, 0], self.e[0, :, 1].max(), self.e[-1, :, 1].min()
self.vbo = glvbo.VBO(self.e)
self.count = self.vbo.shape[1]
self.scroll = 0
self.number_of_arm = 24
self.linerange = [(self.e[li, :, 1].max(), self.e[-li, :, 1].min()) for li in range(self.vbo.shape[0])]
self.showMaximized()

starfield simulation rendering blank [closed]

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Closed 3 years ago.
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How to python debug opengl starfield simulation that drawing a black screen? The code seems ok, but obviously something is off. Are there any additional functions such as glGetError that can verify variables to assist in debugging? I believe I have hurdled, coded correctly a glMapBufferRange function call.
UPDATE: With excellent support by Rabbid76 the program is now rendering the same as expected results. Thank you very much!
Expected output:
Support files: starfield_support.zip
Ported from: starfield.cpp
source code:
#!/usr/bin/python3
import sys
import time
import ctypes
fullscreen = True
sys.path.append("./shared")
from sbmloader import SBMObject # location of sbm file format loader
from ktxloader import KTXObject # location of ktx file format loader
from textoverlay import OVERLAY_
from shader import shader_load, link_from_shaders
from sbmath import m3dDegToRad, m3dRadToDeg, m3dTranslateMatrix44, m3dRotationMatrix44, \
m3dMultiply, m3dOrtho, m3dPerspective, rotation_matrix, translate, m3dScaleMatrix44, \
scale, m3dLookAt, normalize
try:
from OpenGL.GLUT import *
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.raw.GL.ARB.vertex_array_object import glGenVertexArrays, glBindVertexArray
except:
print ('''
ERROR: PyOpenGL not installed properly.
''')
sys.exit()
import numpy as np
from math import cos, sin, floor
import glm
identityMatrix = [1,0,0,0, 0,1,0,0, 0,0,1,0, 0,0,0,1]
myobject = SBMObject()
ktxobject = KTXObject()
overlay = OVERLAY_()
render_prog = GLuint(0)
star_texture = GLuint(0)
star_vao = GLuint(0)
star_buffer = GLuint(0)
debugcontext=True
errors_only=True
class UNIFORMS_:
time=0
proj_matrix=0
uniforms = UNIFORMS_()
NUM_STARS = 2000
import random
random.seed (0x13371337)
def random_float():
return random.random()
def checkGLError():
status = glGetError()
if status != GL_NO_ERROR:
raise RuntimeError('gl error %s' % (status,))
#GLDEBUGPROC
def CB_OpenGL_DebugMessage(source, type, id, severity, length, message, userParam):
msg = message[0:length]
print('debug:', msg)
class Scene:
def __init__(self, width, height):
global render_prog
global star_vao
global star_buffer
global uniforms
global star_texture
self.width = width
self.height = height
vs = GLuint(0)
fs = GLuint(0)
fs_source = '''
#version 410 core
layout (location = 0) out vec4 color;
uniform sampler2D tex_star;
flat in vec4 starColor;
void main(void)
{
color = starColor * texture(tex_star, gl_PointCoord);
//color.r = 1.0;
}
'''
vs_source = '''
#version 410 core
layout (location = 0) in vec4 position;
layout (location = 1) in vec4 color;
uniform float time;
uniform mat4 proj_matrix;
flat out vec4 starColor;
void main(void)
{
vec4 newVertex = position;
newVertex.z += time;
newVertex.z = fract(newVertex.z);
float size = (20.0 * newVertex.z * newVertex.z);
starColor = smoothstep(1.0, 7.0, size) * color;
newVertex.z = (999.9 * newVertex.z) - 1000.0;
gl_Position = proj_matrix * newVertex;
gl_PointSize = size;
}
'''
vs = glCreateShader(GL_VERTEX_SHADER)
glShaderSource(vs, vs_source)
glCompileShader(vs)
if not glGetShaderiv(vs, GL_COMPILE_STATUS):
print( 'compile error:' )
print( glGetShaderInfoLog(vs) )
fs = glCreateShader(GL_FRAGMENT_SHADER)
glShaderSource(fs, fs_source)
glCompileShader(fs)
if not glGetShaderiv(fs, GL_COMPILE_STATUS):
print( 'compile error:' )
print( glGetShaderInfoLog(fs) )
render_prog = glCreateProgram()
glAttachShader(render_prog, vs)
glAttachShader(render_prog, fs)
glLinkProgram(render_prog)
if not glGetProgramiv(render_prog, GL_LINK_STATUS):
print( 'link error:' )
print( glGetProgramInfoLog(render_prog) )
glDeleteShader(vs)
glDeleteShader(fs)
uniforms.time = glGetUniformLocation(render_prog, "time")
uniforms.proj_matrix = glGetUniformLocation(render_prog, "proj_matrix")
star_texture = ktxobject.ktx_load("star.ktx")
glGenVertexArrays(1, star_vao)
glBindVertexArray(star_vao)
class star_t:
position = glm.vec3
color = glm.vec3
size_star_t = ctypes.sizeof(ctypes.c_float) * 6; # same as glm.sizeof(glm.vec3) * 2
glGenBuffers(1, star_buffer)
glBindBuffer(GL_ARRAY_BUFFER, star_buffer)
glBufferData(GL_ARRAY_BUFFER, NUM_STARS * size_star_t, None, GL_STATIC_DRAW)
star = glMapBufferRange(GL_ARRAY_BUFFER, 0, NUM_STARS * size_star_t, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT)
m = (GLfloat * 6 * NUM_STARS).from_address(star)
for i in range(0, 1000):
m[i][0] = (random_float() * 2.0 - 1.0) * 100.0
m[i][1] = (random_float() * 2.0 - 1.0) * 100.0
m[i][2] = random_float()
m[i][3] = 0.8 + random_float() * 0.2
m[i][4] = 0.8 + random_float() * 0.2
m[i][5] = 0.8 + random_float() * 0.2
glUnmapBuffer(GL_ARRAY_BUFFER)
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, size_star_t, None)
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, size_star_t, ctypes.c_void_p(glm.sizeof(glm.vec3) ) )
glEnableVertexAttribArray(0)
glEnableVertexAttribArray(1)
def display(self):
global render_prog
global star_vao
global uniforms
currentTime = time.time()
black = [ 0.0, 0.0, 0.0, 0.0 ]
one = [ 1.0 ]
t = currentTime
proj_matrix = (GLfloat * 16)(*identityMatrix)
proj_matrix = m3dPerspective(m3dDegToRad(50.0), float(self.width) / float(self.height), 0.1, 1000.0)
t *= 0.1
t -= floor(t)
glViewport(0, 0, self.width, self.height)
glClearBufferfv(GL_COLOR, 0, black)
glClearBufferfv(GL_DEPTH, 0, one)
glUseProgram(render_prog)
glUniform1f(uniforms.time, t)
glUniformMatrix4fv(uniforms.proj_matrix, 1, GL_FALSE, proj_matrix)
glEnable(GL_BLEND)
glBlendFunc(GL_ONE, GL_ONE)
glBindVertexArray(star_vao)
glEnable(GL_PROGRAM_POINT_SIZE)
glDrawArrays(GL_POINTS, 0, NUM_STARS)
glutSwapBuffers()
def reshape(self, width, height):
self.width = width
self.height = height
def keyboard(self, key, x, y ):
global fullscreen
print ('key:' , key)
if key == b'\x1b': # ESC
sys.exit()
elif key == b'f' or key == b'F': #fullscreen toggle
if (fullscreen == True):
glutReshapeWindow(512, 512)
glutPositionWindow(int((1360/2)-(512/2)), int((768/2)-(512/2)))
fullscreen = False
else:
glutFullScreen()
fullscreen = True
def init(self):
pass
def timer(self, blah):
glutPostRedisplay()
glutTimerFunc( int(1/60), self.timer, 0)
time.sleep(1/60.0)
if __name__ == '__main__':
glutInit()
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH)
glutInitWindowSize(512, 512)
glutInitContextVersion(4,1)
glutInitContextProfile(GLUT_CORE_PROFILE)
w1 = glutCreateWindow('OpenGL SuperBible - Starfield')
if debugcontext:
glDebugMessageCallback(CB_OpenGL_DebugMessage, None)
if errors_only:
glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, None, GL_FALSE)
glDebugMessageControl(GL_DEBUG_SOURCE_API, GL_DEBUG_TYPE_ERROR, GL_DONT_CARE, 0, None, GL_TRUE)
else:
glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, None, GL_TRUE)
glEnable(GL_DEBUG_OUTPUT)
glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS)
glDebugMessageInsert(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_MARKER, 0, GL_DEBUG_SEVERITY_NOTIFICATION, -1, "Starting debug messaging service")
glutInitWindowPosition(int((1360/2)-(512/2)), int((768/2)-(512/2)))
fullscreen = False
#glutFullScreen()
scene = Scene(512,512)
glutReshapeFunc(scene.reshape)
glutDisplayFunc(scene.display)
glutKeyboardFunc(scene.keyboard)
glutIdleFunc(scene.display)
#glutTimerFunc( int(1/60), scene.timer, 0)
scene.init()
glutMainLoop()

How to python debug opengl [...]
Those days it is common to generate debug output when debugging OpenGL.
The Kronos wiki page Debug Output tells everything about it what you've to know.
A debug message callback is specified by glDebugMessageCallback. The debug output has to be enabled by glEnable(GL_DEBUG_OUTPUT). Synchronous outputs can are generated when glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS) is enabled.
Which outputs are generated can be set by glDebugMessageControl in detail.
To activate the debug output you've to generate a debug call back function with the decorator #GLDEBUGPROC:
#GLDEBUGPROC
def CB_OpenGL_DebugMessage(source, type, id, severity, length, message, userParam):
msg = message[0:length]
print('debug:', msg)
Activate the debug callbacks after creating the window:
if __name__ == '__main__':
glutInit()
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH)
glutInitWindowSize(512, 512)
w1 = glutCreateWindow('OpenGL SuperBible - Starfield')
if debugcontext:
glDebugMessageCallback(CB_OpenGL_DebugMessage, None)
if errors_only:
glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, None, GL_FALSE)
glDebugMessageControl(GL_DEBUG_SOURCE_API, GL_DEBUG_TYPE_ERROR, GL_DONT_CARE, 0, None, GL_TRUE)
else:
glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, None, GL_TRUE)
glEnable(GL_DEBUG_OUTPUT)
glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS)
glDebugMessageInsert(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_MARKER, 0, GL_DEBUG_SEVERITY_NOTIFICATION, -1, "Starting debug messaging service")
glutInitWindowPosition(int((1360/2)-(512/2)), int((768/2)-(512/2)))
fullscreen = False
#glutFullScreen()
scene = Scene(512,512)
glutReshapeFunc(scene.reshape)
glutDisplayFunc(scene.display)
glutKeyboardFunc(scene.keyboard)
glutIdleFunc(scene.display)
#glutTimerFunc( int(1/60), scene.timer, 0)
scene.init()
glutMainLoop()

How to implement zoom towards mouse like in 3dsMax?

I'm trying to mimick the 3dsmax behaviour when you zoom in/out by moving the mouse wheel. In 3ds max this zooming will be towards the mouse position. So far I've come up with this little mcve:
import math
from ctypes import c_void_p
import numpy as np
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
from glm import *
class Camera():
def __init__(
self,
eye=None, target=None, up=None,
fov=None, near=0.1, far=100000,
**kwargs
):
self.eye = vec3(eye) or vec3(0, 0, 1)
self.target = vec3(target) or vec3(0, 0, 0)
self.up = vec3(up) or vec3(0, 1, 0)
self.original_up = vec3(self.up)
self.fov = fov or radians(45)
self.near = near
self.far = far
def update(self, aspect):
self.view = lookAt(self.eye, self.target, self.up)
self.projection = perspective(self.fov, aspect, self.near, self.far)
def zoom(self, *args):
delta = -args[1] * 0.1
distance = length(self.target - self.eye)
self.eye = self.target + (self.eye - self.target) * (delta + 1)
def zoom_towards_cursor(self, *args):
x = args[2]
y = args[3]
v = glGetIntegerv(GL_VIEWPORT)
viewport = vec4(float(v[0]), float(v[1]), float(v[2]), float(v[3]))
height = viewport.z
p0 = vec3(x, height - y, 0.0)
p1 = vec3(x, height - y, 1.0)
v1 = unProject(p0, self.view, self.projection, viewport)
v2 = unProject(p1, self.view, self.projection, viewport)
world_from = vec3(
(-v1.z * (v2.x - v1.x)) / (v2.z - v1.z) + v1.x,
(-v1.z * (v2.y - v1.y)) / (v2.z - v1.z) + v1.y,
0.0
)
self.eye.z = self.eye.z * (1.0 + 0.1 * args[1])
view = lookAt(self.eye, self.target, self.up)
v1 = unProject(p0, view, self.projection, viewport)
v2 = unProject(p1, view, self.projection, viewport)
world_to = vec3(
(v1.z * (v2.x - v1.x)) / (v2.z - v1.z) + v1.x,
(-v1.z * (v2.y - v1.y)) / (v2.z - v1.z) + v1.y,
0.0
)
offset = world_to - world_from
print(self.eye.z, world_from, world_to, offset)
self.eye += offset
self.target += offset
class GlutController():
def __init__(self, camera):
self.camera = camera
self.zoom = self.camera.zoom
def glut_mouse_wheel(self, *args):
self.zoom(*args)
class MyWindow:
def __init__(self, w, h):
self.width = w
self.height = h
glutInit()
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH)
glutInitWindowSize(w, h)
glutCreateWindow('OpenGL Window')
self.startup()
glutReshapeFunc(self.reshape)
glutDisplayFunc(self.display)
glutMouseWheelFunc(self.controller.glut_mouse_wheel)
glutKeyboardFunc(self.keyboard_func)
glutIdleFunc(self.idle_func)
def keyboard_func(self, *args):
try:
key = args[0].decode("utf8")
if key == "\x1b":
glutLeaveMainLoop()
if key in ['1']:
self.controller.zoom = self.camera.zoom
print("Using normal zoom")
elif key in ['2']:
self.controller.zoom = self.camera.zoom_towards_cursor
print("Using zoom towards mouse")
except Exception as e:
import traceback
traceback.print_exc()
def startup(self):
glEnable(GL_DEPTH_TEST)
aspect = self.width / self.height
params = {
"eye": vec3(10, 10, 10),
"target": vec3(0, 0, 0),
"up": vec3(0, 1, 0)
}
self.cameras = [
Camera(**params)
]
self.camera = self.cameras[0]
self.model = mat4(1)
self.controller = GlutController(self.camera)
def run(self):
glutMainLoop()
def idle_func(self):
glutPostRedisplay()
def reshape(self, w, h):
glViewport(0, 0, w, h)
self.width = w
self.height = h
def display(self):
self.camera.update(self.width / self.height)
glClearColor(0.2, 0.3, 0.3, 1.0)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
glMatrixMode(GL_PROJECTION)
glLoadIdentity()
gluPerspective(degrees(self.camera.fov), self.width / self.height, self.camera.near, self.camera.far)
glMatrixMode(GL_MODELVIEW)
glLoadIdentity()
e = self.camera.eye
t = self.camera.target
u = self.camera.up
gluLookAt(e.x, e.y, e.z, t.x, t.y, t.z, u.x, u.y, u.z)
glColor3f(1, 1, 1)
glBegin(GL_LINES)
for i in range(-5, 6):
if i == 0:
continue
glVertex3f(-5, 0, i)
glVertex3f(5, 0, i)
glVertex3f(i, 0, -5)
glVertex3f(i, 0, 5)
glEnd()
glBegin(GL_LINES)
glColor3f(1, 1, 1)
glVertex3f(-5, 0, 0)
glVertex3f(0, 0, 0)
glVertex3f(0, 0, -5)
glVertex3f(0, 0, 0)
glColor3f(1, 0, 0)
glVertex3f(0, 0, 0)
glVertex3f(5, 0, 0)
glColor3f(0, 1, 0)
glVertex3f(0, 0, 0)
glVertex3f(0, 5, 0)
glColor3f(0, 0, 1)
glVertex3f(0, 0, 0)
glVertex3f(0, 0, 5)
glEnd()
glutSwapBuffers()
if __name__ == '__main__':
window = MyWindow(800, 600)
window.run()
In this snippet you can switch between 2 zooming modes by pressing keys '1' or '2' keys.
When pressing '1' I'm doing an standard zooming, so far so good.
Problem is when pressing '2', in this case I've tried to adapt code from this thread to python/pyopengl/pygml but because I didn't understand very well the underlying maths of that answer I don't know very well how to fix the bad behaviour.
How would you fix the posted code so it will zoom in/out towards the mouse properly like 3dsmax?

A possible solution is to move the camera along a ray, from the camera position through the cursor (mouse) position and to move the target position in parallel.
self.eye = self.eye + ray_cursor * delta
self.target = self.target + ray_cursor * delta
For this the window position of the cursor has to be "un-projected" (unProject).
Calculate the cursor position in world space (e.g. on the far plane):
pt_wnd = vec3(x, height - y, 1.0)
pt_world = unProject(pt_wnd, self.view, self.projection, viewport)
The ray from the eye position through the cursor is given by the the normalized vector from the eye position to the world space cursor position:
ray_cursor = normalize(pt_world - self.eye)
There is an issue in your code when you get the window height from the viewport rectangle, because the height is the .w component rather than the .z component:
v = glGetIntegerv(GL_VIEWPORT)
viewport = vec4(float(v[0]), float(v[1]), float(v[2]), float(v[3]))
width = viewport.z
height = viewport.w
Full code listing of the function zoom_towards_cursor:
def zoom_towards_cursor(self, *args):
x = args[2]
y = args[3]
v = glGetIntegerv(GL_VIEWPORT)
viewport = vec4(float(v[0]), float(v[1]), float(v[2]), float(v[3]))
width = viewport.z
height = viewport.w
pt_wnd = vec3(x, height - y, 1.0)
pt_world = unProject(pt_wnd, self.view, self.projection, viewport)
ray_cursor = normalize(pt_world - self.eye)
delta = -args[1]
self.eye = self.eye + ray_cursor * delta
self.target = self.target + ray_cursor * delta
See also Python OpenGL 4.6, GLM navigation
Preview:

How to implement camera pan like in 3dsMax?

What are the necessary maths to achieve the camera panning effect that's used in 3ds max?
In 3ds max the distance between the cursor and the mesh will always remain the same throughout the entire movement (mouse_down+mouse_motion+mouse_up).
My naive and failed attempt has been trying to move the camera on the plane XY by using dt (frame time) multiplied by some hardcoded constant and the result is really ugly and uintuitive.
The code I've got so far is:
def glut_mouse(self, button, state, x, y):
self.last_mouse_pos = vec2(x, y)
self.mouse_down_pos = vec2(x, y)
def glut_motion(self, x, y):
pos = vec2(x, y)
move = self.last_mouse_pos - pos
self.last_mouse_pos = pos
self.pan(move)
def pan(self, delta):
forward = vec3.normalize(self.target - self.eye)
right = vec3.normalize(vec3.cross(forward, self.up))
up = vec3.normalize(vec3.cross(forward, right))
if delta.x:
right = right*delta.x
if delta.y:
up = up*delta.y
self.eye+=(right+up)
self.target+=(right+up)
Could you explain how the maths of camera panning in 3dsmax work?
EDIT:
My question has already been answered initially by #Rabbid76 but there's still one case where his algorithm won't work properly. It doesn't handle properly the case where you panning is started from empty space (said otherwise, when depth buffer value takes the far value=1.0). In 3dsmax camera panning is handled correctly in all situations, no matter which value of the depth buffer.

Your solution would work at orthographic projection, but it fails at perspective projection. Note, at Perspective Projection the projection matrix describes the mapping from 3D points in the world as they are seen from of a pinhole camera, to 2D points of the viewport.
The amount of displacement for the eye and target position depends on the depth of the object which is dragged on the viewport.
If the object is close to the eye position, then a translation on the viewport leads to a small displacement of the eye and target positions:
If the distance from the object to the eye is far, then a translation on the viewport leads to a large displacement of the eye and target positions:
To do what you want you have to know the size of the viewport, the view matrix and the projection matrix:
self.width # width of the viewport
self.height # height of the viewport
self.view # view matrix
self.proj # prjection matrix
Change the pane method, so that it receives the new and old mouse position. Note y axis has to be flipped (self.height-y). Get the depth of the hit point (object) by glReadPixels using the format type GL_DEPTH_COMPONENT:
def glut_mouse(self, button, state, x, y):
self.drag = state == GLUT_DOWN
self.last_mouse_pos = glm.vec2(x, self.height-y)
self.mouse_down_pos = glm.vec2(x, self.height-y)
if self.drag:
depth_buffer = glReadPixels(x, self.height-y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT)
self.last_depth = depth_buffer[0][0]
print(self.last_depth)
def glut_motion(self, x, y):
if not self.drag:
return
old_pos = self.last_mouse_pos
new_pos = glm.vec2(x, self.__vp_size[1]-y)
self.last_mouse_pos = new_pos
self.pan(self.last_depth, old_pos, new_pos)
def pan(self, depth, old_pos, new_pos):
# .....
The mouse position gives a position in window space, where the z coordinate is the depth of the hit point respectively object:
wnd_from = glm.vec3(old_pos[0], old_pos[1], float(depth))
wnd_to = glm.vec3(new_pos[0], new_pos[1], float(depth))
This positions can be transformed to world space by glm.unProject:
vp_rect = glm.vec4(0, 0, self.width, self.height)
world_from = glm.unProject(wnd_from, self.view, self.proj, vp_rect)
world_to = glm.unProject(wnd_to, self.view, self.proj, vp_rect)
The world space displacement of the eye and target position is the distance from the old to the new world position:
world_vec = world_to - world_from
Finally calculate the new eye and target position and update the view matrix:
self.eye = self.eye - world_vec
self.target = self.target - world_vec
self.view = glm.lookAt(self.eye, self.target, self.up)
See also Python OpenGL 4.6, GLM navigation
I tested the code with the following example:
Preview:
Full python code:
import os
import math
import numpy as np
import glm
from OpenGL.GLUT import *
from OpenGL.GL import *
from OpenGL.GL.shaders import *
from OpenGL.arrays import *
from ctypes import c_void_p
class MyWindow:
__caption = 'OpenGL Window'
__vp_size = [800, 600]
__vp_valid = False
__glut_wnd = None
__glsl_vert = """
#version 450 core
layout (location = 0) in vec3 a_pos;
layout (location = 1) in vec3 a_nv;
layout (location = 2) in vec4 a_col;
out vec3 v_pos;
out vec3 v_nv;
out vec4 v_color;
uniform mat4 u_proj;
uniform mat4 u_view;
uniform mat4 u_model;
void main()
{
mat4 model_view = u_view * u_model;
mat3 normal = transpose(inverse(mat3(model_view)));
vec4 view_pos = model_view * vec4(a_pos.xyz, 1.0);
v_pos = view_pos.xyz;
v_nv = normal * a_nv;
v_color = a_col;
gl_Position = u_proj * view_pos;
}
"""
__glsl_frag = """
#version 450 core
out vec4 frag_color;
in vec3 v_pos;
in vec3 v_nv;
in vec4 v_color;
void main()
{
vec3 N = normalize(v_nv);
vec3 V = -normalize(v_pos);
float ka = 0.1;
float kd = max(0.0, dot(N, V)) * 0.9;
frag_color = vec4(v_color.rgb * (ka + kd), v_color.a);
}
"""
__program = None
__vao = None
__vbo = None
__no_vert = 0
def __init__(self, w, h):
self.__vp_size = [w, h]
glutInit()
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH)
glutInitWindowSize(self.__vp_size[0], self.__vp_size[1])
__glut_wnd = glutCreateWindow(self.__caption)
self.__program = compileProgram(
compileShader( self.__glsl_vert, GL_VERTEX_SHADER ),
compileShader( self.__glsl_frag, GL_FRAGMENT_SHADER ),
)
self.___attrib = { a : glGetAttribLocation (self.__program, a) for a in ['a_pos', 'a_nv', 'a_col'] }
print(self.___attrib)
self.___uniform = { u : glGetUniformLocation (self.__program, u) for u in ['u_model', 'u_view', 'u_proj'] }
print(self.___uniform)
v = [ -1,-1,1, 1,-1,1, 1,1,1, -1,1,1, -1,-1,-1, 1,-1,-1, 1,1,-1, -1,1,-1 ]
c = [ 1.0, 0.0, 0.0, 1.0, 0.5, 0.0, 1.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0 ]
n = [ 0,0,1, 1,0,0, 0,0,-1, -1,0,0, 0,1,0, 0,-1,0 ]
e = [ 0,1,2,3, 1,5,6,2, 5,4,7,6, 4,0,3,7, 3,2,6,7, 1,0,4,5 ]
attr_array = []
for si in range(6):
for vi in range(6):
ci = [0, 1, 2, 0, 2, 3][vi]
i = si*4+ci
attr_array.extend( [ v[e[i]*3], v[e[i]*3+1], v[e[i]*3+2] ] )
attr_array.extend( [ n[si*3], n[si*3+1], n[si*3+2] ] )
attr_array.extend( [ c[si*3], c[si*3+1], c[si*3+2], 1 ] );
self.__no_vert = len(attr_array) // 10
vertex_attributes = np.array(attr_array, dtype=np.float32)
self.__vbo = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, self.__vbo)
glBufferData(GL_ARRAY_BUFFER, vertex_attributes, GL_STATIC_DRAW)
self.__vao = glGenVertexArrays(1)
glBindVertexArray(self.__vao)
glVertexAttribPointer(0, 3, GL_FLOAT, False, 10*vertex_attributes.itemsize, None)
glEnableVertexAttribArray(0)
glVertexAttribPointer(1, 3, GL_FLOAT, False, 10*vertex_attributes.itemsize, c_void_p(3*vertex_attributes.itemsize))
glEnableVertexAttribArray(1)
glVertexAttribPointer(2, 4, GL_FLOAT, False, 10*vertex_attributes.itemsize, c_void_p(6*vertex_attributes.itemsize))
glEnableVertexAttribArray(2)
glEnable(GL_DEPTH_TEST)
glUseProgram(self.__program)
glutReshapeFunc(self.__reshape)
glutDisplayFunc(self.__mainloop)
glutMouseFunc(self.glut_mouse)
glutMotionFunc(self.glut_motion)
self.drag = False
self.eye = glm.vec3(-3, -7, 6)
self.target = glm.vec3(0, 0, 0)
self.up = glm.vec3(0, 0, 1)
self.near = 0.1
self.far = 100.0
aspect = self.__vp_size[0]/self.__vp_size[1]
self.proj = glm.perspective(glm.radians(90.0), aspect, self.near, self.far)
self.view = glm.lookAt(self.eye, self.target, self.up)
self.model = glm.mat4(1)
def run(self):
self.__starttime = 0
self.__starttime = self.elapsed_ms()
glutMainLoop()
def elapsed_ms(self):
return glutGet(GLUT_ELAPSED_TIME) - self.__starttime
def __reshape(self, w, h):
self.__vp_valid = False
def __mainloop(self):
if not self.__vp_valid:
self.width = glutGet(GLUT_WINDOW_WIDTH)
self.height = glutGet(GLUT_WINDOW_HEIGHT)
self.__vp_size = [self.width, self.height]
self.__vp_valid = True
aspect = self.width / self.height
self.proj = glm.perspective(glm.radians(90.0), aspect, self.near, self.far)
glUniformMatrix4fv(self.___uniform['u_proj'], 1, GL_FALSE, glm.value_ptr(self.proj) )
glUniformMatrix4fv(self.___uniform['u_view'], 1, GL_FALSE, glm.value_ptr(self.view) )
glUniformMatrix4fv(self.___uniform['u_model'], 1, GL_FALSE, glm.value_ptr(self.model) )
glClearColor(0.2, 0.3, 0.3, 1.0)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
glDrawArrays(GL_TRIANGLES, 0, self.__no_vert)
glutSwapBuffers()
glutPostRedisplay()
def glut_mouse(self, button, state, x, y):
self.drag = state == GLUT_DOWN
self.last_mouse_pos = glm.vec2(x, self.height-y)
self.mouse_down_pos = glm.vec2(x, self.height-y)
if self.drag:
depth_buffer = glReadPixels(x, self.height-y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT)
self.last_depth = depth_buffer[0][0]
print(self.last_depth)
def glut_motion(self, x, y):
if not self.drag:
return
old_pos = self.last_mouse_pos
new_pos = glm.vec2(x, self.__vp_size[1]-y)
self.last_mouse_pos = new_pos
self.pan(self.last_depth, old_pos, new_pos)
def pan(self, depth, old_pos, new_pos):
wnd_from = glm.vec3(old_pos[0], old_pos[1], float(depth))
wnd_to = glm.vec3(new_pos[0], new_pos[1], float(depth))
vp_rect = glm.vec4(0, 0, self.width, self.height)
world_from = glm.unProject(wnd_from, self.view, self.proj, vp_rect)
world_to = glm.unProject(wnd_to, self.view, self.proj, vp_rect)
world_vec = world_to - world_from
self.eye = self.eye - world_vec
self.target = self.target - world_vec
self.view = glm.lookAt(self.eye, self.target, self.up)
window = MyWindow(800, 600)
window.run()

[...] but there's still one case where his algorithm won't work properly. It doesn't handle properly the case where you panning is started from empty space [...]
In the solution the depth of the object is taken from the depth buffer, at that position, where the mouse click occurs. If this is the "empty space", a position where no object was drawn, the depth is the maximum of the depth range (in common 1). This leads to a rapid paining.
A solution or workaround would be use the depth of an representative position of the scene. e.g. the origin of the world:
pt_drag = glm.vec3(0, 0, 0)
Of course this may not lead to a proper result in each case. If the objects of the scene are not around the origin of the world, this approach will fail. I recommend to calculate the center of the axis aligned bounding box of the scene. Use this point for the representative "depth":
box_min = ... # glm.vec3
box_max = ... # glm.vec3
pt_drag = (box_min + box_max) / 2
The depth of a point can computed by the transformation with the view and projection matrix and a final perspective divide:
o_clip = self.proj * self.view * glm.vec4(pt_drag, 1)
o_ndc = glm.vec3(o_clip) / o_clip.w
This can be applied to the function glut_mouse:
def glut_mouse(self, button, state, x, y):
self.drag = state == GLUT_DOWN
self.last_mouse_pos = glm.vec2(x, self.height-y)
self.mouse_down_pos = glm.vec2(x, self.height-y)
if self.drag:
depth_buffer = glReadPixels(x, self.height-y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT)
self.last_depth = depth_buffer[0][0]
if self.last_depth == 1:
pt_drag = glm.vec3(0, 0, 0)
o_clip = self.proj * self.view * glm.vec4(pt_drag, 1)
o_ndc = glm.vec3(o_clip) / o_clip.w
if o_ndc.z > -1 and o_ndc.z < 1:
self.last_depth = o_ndc.z * 0.5 + 0.5
Preview:
The key to a well feeling solution is to find the "correct" depth. At perspective projection the dragging, where the mouse movement effects the object in a 1:1 motion, projected on the viewport, only works correctly for a well defined depth. Objects with different depths are displaced by a different scale when they projected on the viewport, that's the "nature" of perspective.
To find the "correct" depth, there are different possibilities, which depend on your needs:
Reading the depth from the depth buffer at the current mouse position:
depth_buffer = glReadPixels(x, self.height-y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT)
self.last_depth = depth_buffer[0][0]
Get the minimum and maximum depth of the depth buffer (except the value for the far plane, 1.0) and calculate the mean depth. Of course the entire depth buffer has to be investigated in this case:
d_buf = glReadPixels(0, 0, self.width, self.height, GL_DEPTH_COMPONENT, GL_FLOAT)
d_vals = [float(d_buf[i][j]) for i in range(self.width) for j in range(self.height) if d_buf[i][j] != 1]
if len(d_vals) > 0:
self.last_depth = (min(d_vals) + max(d_vals)) / 2
Use the origin of the world:
pt_drag = glm.vec3(0, 0, 0)
o_clip = self.proj * self.view * glm.vec4(pt_drag, 1)
o_ndc = glm.vec3(o_clip) / o_clip.w
if o_ndc.z > -1 and o_ndc.z < 1:
self.last_depth = o_ndc.z * 0.5 + 0.5
Calculating the center of the bounding box of the scene.
Implement a raycasting, which identifies an object by a ray, which starts at the point of view a runs trough the cursor (mouse) position. This algorithm can be advanced by identifying the object which is "closest" to the ray, when no object is hit.
See also Python OpenGL 4.6, GLM navigation